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function [engine, ll] = enter_evidence(engine, evidence, nsamples)
% ENTER_EVIDENCE Add the specified evidence to the network (likelihood_weighting)
% [engine, ll] = enter_evidence(engine, evidence, nsamples)
% evidence{i} = [] if if X(i) is hidden, and otherwise contains its observed value (scalar or column vector)
%
% If nsamples is not specified, the value specified when the engine was created will be used.
% ll (log-likelihood) is set to [].
ll = [];
if nargin < 3, nsamples = engine.nsamples; end
bnet = bnet_from_engine(engine);
N = length(bnet.dag);
samples = cell(nsamples, N);
weights = zeros(1, nsamples);
ns = bnet.node_sizes;
original_evidence = evidence;
observed = ~isemptycell(original_evidence);
for s=1:nsamples
evidence = original_evidence(:); % must be a column vector
w = 1;
for i=1:N
ps = parents(bnet.dag, i);
e = bnet.equiv_class(i);
if observed(i)
p = exp(log_prob_node(bnet.CPD{e}, evidence(i), evidence(ps)));
w = w * p;
else
x = sample_node(bnet.CPD{e}, evidence(ps));
evidence{i} = x;
end
end
samples(s,:) = evidence;
weights(s) = w;
end
engine.samples = samples;
engine.weights = weights;
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